I will submit a payment online

I will submit a payment online using their website and while the payment is pending they will continue to call me CONSTANTLY. At least 3-5 times in one day and even on Sundays. When I do answer the line it gets directed over to an agent who tells me to disregard the call because I have a payment pending. This is a HUGE hassle. My phone is ringing CONSTANTLY from Sallie Mae even after I have made my payment and it is pending.